Air Pollution Impacts

Lassen Volcanic National Park

Natural and scenic resources in Lassen Volcanic National Park (NP) are susceptible to the harmful effects of air pollution. Nitrogen, sulfur, toxics, ozone, and fine particles impact natural resources such as wildlife, surface waters, and vegetation, and scenic resources such as visibility. Click on the tabs below to learn more about air pollutants and their impacts on natural and scenic resources at Lassen Volcanic NP.

Nitrogen & Sulfur

Toxics & Mercury

Ozone

Visibility

High elevation lakes, including Crags Lake, at Lassen Volcanic NP in California are particularly sensitive to nitrogen and sulfur deposition.

Nitrogen (N) and sulfur (S) compounds deposited from air pollution can harm surface waters, soils, and vegetation. High elevation ecosystems at the park are particularly sensitive to N and S deposition. These systems receive more deposition than lower elevation areas because of greater amounts of snow and rain. Additionally, short growing seasons and shallow soils limit the capacity of soils and plants to buffer or absorb N and S. High elevation lakes at Lassen Volcanic NP are especially sensitive to acidification from N and S deposition and excess N enrichment. Acidification may cause loss of sensitive macroinvertebrates and fish, while enrichment may change plant communities. Both can alter lake and stream diversity (Sullivan et al. 2011a; Sullivan et al. 2011b [pdf, 6.8 MB]; Sullivan et al. 2011c; Sullivan et al. 2011d [pdf, 2.6 MB]).

N deposition may also disrupt soil nutrient cycling and alter plant communities. In some areas of the country increased nitrogen deposition has allowed weedy annual grasses to invade shrublands and grasslands, replacing native plants that evolved under nitrogen-poor conditions. In southern California, increased N deposition has contributed to invasions of annual grasses that have subsequently increased fire risk in shrublands of Joshua Tree NP (Rao et al. 2010).

Volcanic formations at Lassen Volcanic NP, including boiling mud pots and fumaroles, naturally emit sulfur compounds such as sulfur dioxide and hydrogen sulfide. Concentrations of S from volcanic emissions are relatively low and are not known to cause acidification on sensitive resources like high elevation lakes. While at higher concentrations these gases can cause significant human health effects—as they do at Hawai'i Volcanoes NP—such levels are not a concern at Lassen Volcanic NP.

How much nitrogen is too much?

Nitrogen is a fertilizer and some nitrogen is necessary for plants to grow. However, in natural ecosystems, too much nitrogen can disrupt the balance of plant communities, allowing weedy species to grow faster. For example, too much nitrogen causes changes in forest lichen communities, with sensitive species gradually replaced by pollution-tolerant species. The amount of nitrogen that ecosystems can tolerate without significant harm is called the critical load. In California, the critical load for sensitive forest lichen species is about 3.1 kg/ha/yr (Fenn et al. 2010). Nitrogen from air pollution may also upset the balance of alpine lakes at the park. In alpine lakes in the eastern Sierra and the Rocky Mountains, nitrogen levels as low as 1.4 kg/ha/yr promote replacement of sensitive aquatic species with species typical of polluted lakes (Saros et al. 2011). N deposition at Lassen Volcanic NP is relatively low (less than 1 kg/ha/yr), but highly sensitive lakes could be at risk. Critical loads for lake and forest resources can be used to establish goals for ecosystem protection and management.

Studies found detectable levels of airborne toxics including mercury and pesticides in ecosystems at Lassen Volcanic NP, California.

Toxics, including heavy metals like mercury, accumulate in the tissue of organisms. When mercury converts to methylmercury in the environment and enters the food chain, effects can include reduced reproductive success, impaired growth and development, and decreased survival. Other toxic air contaminants of concern include pesticides, industrial by-products, and emerging chemicals such as flame retardants for fabrics. Some of these are known or suspected to cause cancer or other serious health effects in humans and wildlife.

Naturally-occurring ozone in the upper atmosphere absorbs the sun’s harmful ultraviolet rays and helps to protect all life on earth. However, in the lower atmosphere, ozone is an air pollutant, forming when nitrogen oxides from vehicles, power plants, and other sources combine with volatile organic compounds from gasoline, solvents, and vegetation in the presence of sunlight. In addition to causing respiratory problems in people, ozone can injure plants. Ozone enters leaves through pores (stomata), where it can kill plant tissues, causing visible injury, or reduce photosynthesis, growth, and reproduction.

Visitors come to Lassen Volcanic NP to enjoy spectacular volcanic landforms and relatively undisturbed natural resources, including forests, lakes, and streams. Unfortunately, park vistas are sometimes obscured by haze caused by fine particles in the air. Many of the same pollutants that ultimately fall out as nitrogen and sulfur deposition contribute to this haze and visibility impairment. Additionally, organic compounds, soot, and dust reduce visibility. Smoke from nearby forest fires also contributes to particulate matter in the region.

Visibility effects at Lassen Volcanic NP include:

Reduced visibility, at times, due to human-caused haze and fine particles of air pollution, including dust;

Reduction of the average natural visual range from about 160 miles (without pollution) to about 100 miles because of pollution at the park;

Reduction of the visual range to below 55 miles on high pollution days.